Record actuated sound system



Unite RECORD ACTUATED SOUND SYSTEM Application Qctoher 14, 15-954,Serial No. 462,196

4 Claims. (Cl. 179-4001) This invention relates to a record-actuatedsound reproducing system in which the actuation or nonactuation of thesound reproducers is determined by recorded signals. More particularlythe invention relates to a sound reproducing system incorporating anelectrical switching circuit interposed between the soundhead and thereproducer, the switching circuit being motivated by one or more signalsrecorded on the sound record so that the reproducer or reproducers areselectively connected to the sound channel or made inoperative.

The invention is particularly adapted for. use with motion picturemultiple sound track systems although not limited thereto. In suchsystems, the motion picture film is provided with or synchronized with amultiple sound track record, one sound track record of which is usedonly at certain times to provide special effects, such as a large volumeof widely distributed sound emanating from loudspeakers distributedthroughout the auditorium. It has been found, however, that if thesespeakers be left in circuit during their unactuated periods they aresubject to electrical noise such as crosstalkfrorn the other soundchannels and switching clicks, and to background noise, and these noisesare clearly audible to the theatre audience. In the instant invention,in order to eliminate the annoyance of this interference the speakersare automatically disconnected from the circuit and grounded duringunactuated periods.

In general the invention accomplishes the actuation and deactivation ofthe special eiiects or auditorium spakers through the medium of selectedtone signals which are recorded on the special effects sound track alongwith the signal which is to be reproduced, the signals being so recordedas to be ideally merely additive or intermixed without intermodulation.The selected tone signals are abstracted from the circuit and utilizedto operate various relays having alternate positions of operation. Inone position of operation of a selected relay the special eifectsspeakers associated therewith are connected in circuit with thesoundhead actuated by the special effects soundtrack while in the otherposition of operation the speakers are disconnected from this circuitand grounded.

In one embodiment of the invention one selected tone signal and thesound signal to be reproduced are recorded simultaneously on the samesound track and the selected signal operates the relay to connect thespecial effects speakers to the reproducing circuit only during theperiods of occurrence of the selected signal.

In an alternative embodiment of the invention the selected tone signalis recorded only during those periods in which there is no signal to bereproduced. In this instance the relay is actuated by the selected tonesignal to disconnect the speakers or otherwise to make them inoperative.

In still another embodiment a plurality of selected tone signals arerecorded simultaneously with the sound effects signal on the same soundtrack. The presence of any one of the tone signals causes a switchingcircuit to operate to one condition and the absence of the signal causesthe circuit to operate to another condition. The several switchingcircuits switch various reproducing cirtes Patent Q 2,841,654 PatentedJuly 1, 1958 r ai cuits in or out in accordance with the presence orabsence of individual tone signals.

One purpose of this invention is to quiet a sound reproducing systemduring intervals of absence of the sound signal.

Another purpose of this invention is to provide a circuit for switchingan electrical channel in obedience to the presence or absence ofelectrical energy of a selected frequency in that channel.

Another purpose of this invention is to provide a circuit for making anelectrical channel conductive when the channel carries a current of aselected frequency While filtering that frequency from the output.

Another purpose of this invention is to provide a circuit for making anelectrical channel non-conductive when the channel carries a current ofa selected frequency.

Still another purpose of this invention is to provide a circuit forswitching a plurality of reproducing circuits in or out of an audiocircuit in accordance with the presence or absence respectively ofselected ones of a plurality of different frequency tone signals in theaudio circuit.

Further'understanding of this invention may be secured from thedescription and drawings in which:

Figure 1 is a block diagram illustrating use of the invention in a soundreproducing circuit.

Figure 2 is a circuit diagram of a switching and translating circuitused to accomplish the purpose of the invention.

Figure 3 is a circuit diagram of a modification of part of the circuitof Fig. 2.

Figure 4 is a block diagram illustrating the individual control of aplurality of reproducing circuits by separate and distinct tone signals.

Referring now to Fig. l, a strip of motion picture film 11 is providedwith four magnetic sound tracks, one of which is utilized for specialsound effects and which will be referred to hereafter as the soundtrack. Each of the four tracks has its own pickup or magnetic soundhead, the pickup 12 for the special sound effect track only being shownin Fig. 1 since the other three are not pertinent to this description.The magnetic record constituting the sound track under considerationunavoidably contains noise or extraneous cross talk, switching clicksand burns. It also contains the special effects signal alternating withtime periods during which the signal is absent. During these periods thenoise of course persists.

During the periods in which sound eifects modulations in the sound trackoccur they are accompanied in the same sound track by a constantalternating current modulation of a selected frequency of, for example,12,000 cycles. The total resulting current in the sound channel 13constituted by the output conductors of pickup 12 represents intermixingduring recording by methods which form no part of this invention butwhich produce a magnetic record containing both the sound and the tonewithout intentional modulation of either by the other. The recording ofthe constant alternating current of a selected frequency or tone startsat the beginning of recording of each sound signal portion, or perhaps ashort distance before, and terminates at the end of the recording of thesound signal portion. This produces a current in the sound head whichhas an approximately constant value.

After amplification in amplifier M the composite sound and tone signalis applied to a tone switching circuit, represented by rectangle 16,which constitutes the circuit for carrying out the objects of thisinvention. The output conductors 17 of this circuit are connected to afinal amplifier 15 which actuates, through condoctors 19, the speaker orspeakers represented by the symbol 21.

One embodiment of switching circuit 16 is depicted in Fig. 2. The inputconductors 1S and 15" are shunted by a series resonant circuitcomprising inductance 22 and adjustable capacitance 23. The resonantfrequency of this circuit is designedto equal the frequency of the tone,which in this case is 12 kc. The series resonant circuit at resonancegenerates a high voltage of the frequency of the tone at its commonjunction 34. The capacitor 23 is made adjustable to permit tuning formaximum capacitor voltage consistent with minimum interference with thesound efiects signal. ance of coil 22 is made fairly high, an inductanceof 150 mh being found satisfactory for use at 12 kc. The Q of this coilshould be moderate, for example, about 12 for usually-encountered inputline impedances as, for example, a line impedance of 500 ohms. it is,however, necessary that the rejection of this series circuit be high forfrequencies of 8 kc. or less.

A parallel resonant circuit consisting of inductance 24 and adjustablecapacitance 26 is inserted in series with the conductor 15'. Thiscircuit including coil 24 and condenser 26, being in the signal channel,should be rather sharply resonant so as to present little loss atfrequencies of 8 kc. and below. For example a coil 24 of 30 mh. and acapacity 26 varying from .005 to .006 ,uf. is satisfactory when a tonefrequency of 12 kc. is used. Output is derived from this circuit througha conductor 27 which is, in effect, a continuation of conductor 15.Conductor 27 is connected to the forward contact 28 of a single-poledouble-throw relay contact assembly having an armature 29 connected toan output terminal 31. The terminal 31 is connected through theconductor 17, Fig. 1, to the input of amplifier 18. The other switchcontact 32, Fig. 2, is connected to ground through resistor 33.

The shunt resonant circuit including inductance 24 and capacitance 26 isdesigned to resonate at the tone frequency, its adjustment being refinedby use of the adjustable capacitor 26. Adjustment should be made so thatthe circuit presents a very high impedance to the 12 kc. tone whilepresenting low impedance to the signal frequencies of 8 kc. and below.

Actuation of the relay contact arm 29 is effected by coupling thejunction 34 through condenser 36 to a voltage divider 37 which serves asan amplitude control. The voltage divider slider 38 is connected to thecontrol grid 39 of a triode 41 having a shunt resonant circuit in itsanode conductor 42. This shunt resonant circuit consists of inductance43 and capacitor 44 and is designed to resonate at the tone frequency.The anode conductor 42 is connected to a source of positive potentialrepresented by terminal 46. The anode 47 of triode 41 is coupled throughcapacitor 48 to a cascade voltage-doubling rectifier comprising diodes49 and 51 and capacitor 52. The output of the rectifier is connected tothe grid53 of directcoupled amplifier triode 54 having the winding 56 ofa relay 55 in its anode circuit, the relay contact assembly comprisingarmature 29 and contacts 28 and 32. Positive anode potential is securedfrom the common junction 57 of a voltage divider containing resistors 58and 59 energized from terminal 46.

If a system is employed in which the tone is on only when the soundsignal is absent, then the relay contacts must be connected asillustrated in Fig. 3. When the relay coil 56 is deenergized the contactarmature 29 is biased to engage the sound channel contact 28 as shown,but when direct current derived from the 12 kc. tone energizes coil 56the armature is moved to engage contact32, breaking the sound channelcircuit and grounding output terminal 31.

In the operation of the circuit of Fig. 2 a sound signal consisting ofaudible frequencies up to 8 kc., combined with a switch signal having afrequency of 12 kc., is ap plied across the input conductors 15 and 15".The series resonant circuit shunting these conductors is tuned byvariable condenser 23 to secure maximum potential at The induct- 12 kc.at the junction 34. The shunt resonant circuit interposed in series inconductors 15 and 27 is tuned by variable condenser 26 for maximumrejection of the 12 kc. tone frequency with minimum effect on thespecial effects output signal. The combined effect of the series andshunt resonant circuits may be considered to be that of an L-section ofa band rejection filter tuned to reject a band centered at 12 kc., andhaving a slope steep enough not to aifect frequencies of 8 kc. andbelow. The output at relay contact 28 is thus devoid of the 12 kc. tonefrequency but contains substantially unattenuated all other signalfrequencies between zero and 8 kc. which were applied to the inputterminals 15' and 15".

The series resonant circuit consisting of inductance 22 and capacitance23 has low impedance for the 12 kc., frequency signal accompanied byhigh potential at junction 34, with higher impedance for all otherfrequencies. A fraction of the potential of junction 34 is selected byuse of voltage divider 37 to control relay opa oration. Voltage divider37 should have high resistance, for example, 1 megohm. It is desirableto amplify and rectify the 12 kc. tone signal in order to secure enoughpower to operate a relay and it has been found preferable to employ twostages of amplification to insure ample power under all conditions. ofinductance 43 and capacitance 44 improves the selectivity of the firststage of amplification. Crystal diode rectification is employed betweenthe first capacity-coupled stage of amplification and the seconddirect-coupled stage. Tests have shown that this circuit provides amplepower for operating a high impedance relay in the anode circuit oftriode 54.

The circuit of Fig. 4 depicts a system in which a plurality of tonesadditively combined with sound on a single sound effects track areemployed to switch the sound to one or more sound reproducers,alternatively or in concert and in any desired combination. As aspecific example let it be supposed that the sound is to come at onetime from a speaker on a stage, at another later time from a speaker atthe left of the auditorium, at another still later time from a speakerat the right of the auditorium, and at still another succeeding timefrom all three speakers together.

To accomplish these results the sound effects are mixed in the soundtrack as before described, being mixed at one time with a 12 kc. signalor tone, at another time with a 15 kc. tone, at another time with an 18kc. tone, and at still another time with all three tones of 12, 15 and18 kc. When the sound effects are absent all tones are also absent fromthe track. The film 11 carrying the sound track is moved past the pickup12 so that the single sound channel composed of the pickup outputconductors 13 contains electrical energy representing these signals andsound added together as described. This energy is voltage-amplified inamplifier 14. The output conductors 15 of amplifier 14 are connected tothree switching and translating circuits 61, 62 and 63, the inputs ofwhich are connected in parallel. The switching and translating circuit61 is substantially the same as circuit 16 of Fig. 1, described inconnection with Fig. 2, and its various resonant circuits are tuned to12 kc. as described. The switching and translating circuits 62 and 63are similar to circuit 61 except that their resonant circuits are tunedto 15 kc. and 18 kc. respectively,;

The output conductors 17, 64 and 66 are connected through amplifiers 18,67, and 68 to speakers 21, 69 and 71. Speaker 21 is installed on thestage, speaker 69 is installed at the left side of the auditorium, andspeaker 71 is installed'at the right side of the auditorium.

In only one respect does the circuit 61 of Fig. 4 dif-' fer from thecircuit of Fig. 2, namely, in the design of the resnonant circuitdesignated in Fig. 2 as composed of inductance 24 and capacitance 26 inparallel. In circuit 61 this resonant circuit must take the form of abroader band filter or of a low-pass filter, so that all frequencies-The anode trap consisting below 8 kc. are transmitted while the tonefrequencies of 12, and 18 kc. are very highly attenuated. Filters havingthe same requirements must he used in circuits 62 and 63.

In the operation of the circuit of Fig. 4, when the film 11 containingno sound effect signal or tones of any frequency is run past the pickup12, all relays in the three switching and translating circuits 61, 62and 63 remain unoperated and normal, short-circuiting their respectivespeakers 21, 69 and 71. When the sound track contain; sound effectsadmixed with only the 12 kc. tone, the relays in circuit 62 and 63remain normal, deactivating the auditorium speakers 69 and 71. However,the relay 55, Fig. 2, in circuit 61, Fig. 4, is operated by tr e 12 kc.tone, and the relay connects speaker 21 into circuit, so that the soundeffects are heard from the stage. in the neXt part of the film the soundeffects are admixed only with 15 kc. tone. The speakers 21 and 71 arethen shortcircuited while the relay in circuit 62 is operated, causingthe sound to emanate only from the left auditorium speaker 69. In thenext part of the film only the right speaker 71 is connected, and in thefinal part of the film all three relays are simultaneously operated andthe sound is heard from all three speakers at the same time.

What is claimed is:

1. A record-actuated sound reproducing system comprising, a recordmedium having a selected tone signal and signals to be reproducedrecorded on a single sound track thereof, pickup means positioned toconvert the signals recorded on said sound track into correspondingelectrical signals, a signal translating channel having its inputconnected to said pickup means, said signal translating channelincluding a filter network connected in series therein offering a highimpedance to a signal frequency corresponding to that of said selectedtone signal and low impedance to signal frequencies corresponding to thesignals to be reproduced, a resonant network connected in shunt to theinput of said signal translating channel having a low impedance tosignal frequencies corresponding to that of said selected tone signaland high impedance to signal frequencies corresponding to the signals tobe produced, loudspeaker means, switch means connecting said loudspeakermeans to the output of said signal translating channel in one conditionof operation and disconnecting said loudspeaker means from said signaltranslating channel and grounding said loudspeaker means through aresistor in a second condition of operation, and means for deriving apotential from said resonant network for determining the condition ofoperation of said switch means.

2. A record-actuated sound reproducing system comprising, a recordmedium having recorded on a single sound track thereof a selected tonesignal intermixed with signals to be reproduced, pickup means positionedto convert the signals recorded on said sound track into correspondingelectrical signals, a signal translating channel having its inputconnected to said pickup means, said signal translating channelincluding a filter network connected in series therein offering highimpedance to a frequency corresponding to that of said selected tonesignal but low impedance to signal frequencies corresponding to those ofsaid signals to be reproduced, a resonant network connected in shunt tothe input of said signal translating channel having a low impedance to afrequency corresponding to that of said selected tone signal but highimpedance to signal frequencies corresponding to those of said signalsto be reproduced, loudspeaker means, switch means connecting saidloudspeaker means to the output of said signal translating channel in afirst condition of operation and disconnecting said loudspeaker meansfrom said signal translating channel and grounding the loudspeaker meansthrough a resistor in a second condition of operation, means forderiving from said resonant network a potential representative of saidselected tone signal, and means operated by said potential to place saidswitch means in said first condition of operation, said switch meansbeing in said second condition of operation in the absence of saidpotential.

3. A record-actuated sound reproducing system comprising, a recordmedium having recorded on a single sound track thereof a selected tonesignal alternating with signals to be reproduced, pickup meanspositioned to convert the signals recorded on said sound track intocorresponding electrical signals, a signal translating channel havingits input connected to said pickup means, said signal translatingchannel including a filter network connected in series therein offeringhigh impedance to a frequency corresponding to that of said selectedtone signal but offering low impedance to frequencies corresponding tothose of said signals to be reproduced, a resonant network connected inshunt to the input of said signal translating channel having a lowimpedance to a frequency corresponding to that of said selected tonesignal but high impedance to frequencies corresponding to those of saidsignalsto be reproduced, loudspeaker means, switch means connecting saidloudspeaker means to the output of said signal translating channel in afirst condition of operation and disconnecting said loudspeaker meansfrom said signal translating channel and grounding the loudspeaker meansthrough a resistor in a second condition of operation, means forderiving from said resonant network a potential representative of saidselected tone signal, and means operated by said potential to place saidswitch means in said second condition of operation, said switch meansbeing in said first condition of operation in the absence of saidpotential.

4. A record-actuated sound reproducing system comprising, a recordmedium having recorded on a single sound track thereof a plurality ofselected tone signals intermixed with signals to be reproduced, pickupmeans positioned to convert the signals recorded on said sound trackinto corresponding electrical signals, a plurality of signal translatingchannels having their inputs connected to said pickup means, each signaltranslating channel including a low-pass filter connected in seriestherein offering high impedance to all frequencies corresponding tothose of said plurality of selected tone signals but offering lowimpedance to signal frequencies corresponding to those of said signalsto be reproduced, each of said signal translating channels including aresonant network connected in shunt to the input thereof, each of saidresonant networks having a low impedance to a respective frequencycorresponding to that of one of said plurality of selected tone signalsbut high impedance to all other frequencies, a plurality of loudspeakermeans, each of said plurality of signal translating channels includingan associated switch means connecting one of said plurality ofloudspeaker means to the output of the signal translatmg channel in afirst condition of operation and disconnecting and grounding said one ofthe plurality of loudspeaker means through a resistor in a secondcondition of operation, means for deriving from each said secondmentioned resonant network a potential representative of said respectivefrequency of a tone signal, and means operated by said potential toplace said associated switch means in said first condition of operation,said switch means being in said second condition of operation in theabsence of said potential.

References Cited in the file of this patent UNITED STATES PATENTS2,075,861 Mueller Apr. 6, 1937 2,101,121 Wixon Dec. 7, 1937 2,298,618Garity et al Oct. 13, 1942 2,313,867 Garity et al Mar. 16, 19432,361,490 Mueller Oct. 31, 1944 2,427,850 Gehman Sept. 23, 19472,499,587 Kellogg Mar. 7, 1950 2,714,633 Fine Aug. 2, 1955

